This invention relates to a method and apparatus for determining the mechanical properties of a material, such as bone.
A number of situations arise where it is important to assess the mechanical properties of a material without destroying or damaging the material. In some cases, this can be done using simplified techniques as a result of the homogeneity of the material. However, in other cases, the material is not homogenous and therefore simplified techniques do not give accurate results.
For instance, in medical applications, it is frequently desirable to determine the mechanical properties of a material such as bone, but destructive tests of course cannot be used in a living patient. Further, invasive tests are undesirable, and the bone is nonhomogeneous and nonisotropic. These complications present a particular problem in the case of patients suffering from osteoporosis, who are more susceptible to fractures as a result of decreased bone strength. Standard radiographic properties of bone, such as bone mineral density, do not correlate well with bone strength, and therefore are of relatively little use in diagnosing osteoporosis or evaluating the results of treatment for that condition.
Although some treatments for osteoporosis are available that can increase the strength of a patient's bones, the utility of those treatments would be enhanced by a noninvasive method of assessing their effect on the patient's bones. In the past, various methods have been investigated for this purpose, but have failed to solve the problem. For example, radiologic methods such as quantitative computed tomography, single or dual photon absorptiometry, and dual energy X-ray absorptiometry measure the amount and distribution of minerals in bone, but do not directly assess its mechanical qualities. These problems of the prior art are minimized or solved by the method and apparatus of the present invention.